This invention relates to an image forming apparatus.
Conventionally, an imaging forming apparatus such as, e.g., a printer, a photocopier, a facsimile machine, and a multi-functional machine, for example, an electrophotographic printer includes a paper feed mechanism for feeding paper as a medium, an image forming unit for forming a toner image, a fuser for fusing the toner image, a discharging mechanism for discharging the paper, and the like. The discharging mechanism is composed of a face down discharging unit composing a first discharging unit to which printed paper is discharged with a printed side down, and a face up discharging unit composing a second discharging unit capable of discharging various sorts of paper, performing post processing such as, e.g., sorting operation and punching operation and discharging the paper with the printed side up. The paper can be selectively discharged to either the face down discharging unit or the face up discharging unit, by an operator's switching a discharging route. (see, e.g., Japanese Unexamined Patent Publication No. 2000-267544)
With such a conventional electrophotographic printer, however, such paper as moved through the fuser gets curled, i.e., deformed, in a crescent shape, not only because the paper receives heat from a printing side at the time when a toner image is fused but also because a toner is fused on the printing side. There are two types of curling, normal curling, i.e., a concave curling, and reverse curling. For example, in a case of occurrence of large normal curling, even where paper is to be discharged to the face up discharging unit, the paper with large normal curling undesirably goes into the face down discharging unit. As the result, paper jamming occurs, and the paper cannot be discharged properly.